When a covert threat emerges to both the super-spies of S.H.I.E.L.D. and 20 million average people, you'd hope the future of mankind wouldn't rest only on a shield-flinging super soldier, an ex-KGB agent and a guy wearing a pair of metallic wings.

After all, the hallmark of Marvel superhero movies is how their minders have woven them together, like the comics they're based on, in an interconnected universe of characters and storylines. There are offhanded references to Hulk alter-ego Bruce Banner, Iron Man's Stark Industries, the events of The Avengers and yet-to-be-introduced characters such as Dr. Strange.

In this sequel to 2011's Captain America: The First Avenger, World War II Army officer Steve Rogers (Chris Evans) remains a stranger in a strange time—ours. He's an anachronism literally wrapped in the flag, coping with a dividing line between good and evil that's less clear than it was in his era.

It's notable that throughout the Marvel films, few heroes or villains hide their actual identities. In one surreal scene, Rogers visits a Smithsonian exhibit devoted to Captain America. The characters' names are open books; it's their motives that can prove murky. This provocative notion propels the movie's plot.

Instead of wresting away freedom at the point of a spear, the power-mad have laid the groundwork for good people to willingly hand it over out of a desire for security. In our world, it's the specter of shoe bombs and illegal immigration; in Marvel's, it's mutant villains and aliens spilling through an inter-dimensional wormhole.

But there's also a spear-tip in Bucky Barnes (Sebastian Stan), the Winter Soldier of the title. Rogers' wartime buddy has been the muscle behind the remnants of HYDRA, a Nazi-era terrorist organization. The most daunting part of Rogers' mission is discerning friend from foe, trying to divine the intentions of Black Widow (Scarlett Johansson), Nick Fury (Samuel L. Jackson) and S.H.I.E.L.D. agent Alexander Pierce (Robert Redford).

The CGI action sequences are energetic yet hyper-edited, and directors Anthony and Joe Russo know when to diffuse weighty metaphors with self-aware one-liners. Most come from Rogers' repartee with Fury, Black Widow and newcomer The Falcon (Anthony Mackie). My favorite is near the end, a blink-and-you'll-miss-it moment that answers a 20-year-old cinematic riddle.